Experimental Study of DOC-on-Filter using next Generation filter solutions for Non-Road Applications

Upcoming California Tier 5 non-road limits mandate 90% and 75% reductions in NOx and PM respectively, from current Tier 4F emission standards. Similarly, lower NOx and PN/PM limits can be expected from a next round of European Non-Road regulations. To meet these limits, more SCR volume for greater NOx reduction, and better filtration efficiency filters for greater PN/PM reduction, may be required. The challenge is to accommodate larger SCR volume while maintaining oxidation (DOC) and filtration (DPF) functionality of the aftertreatment system within a limited packaging space on non-road machineries. Consolidating DOC and DPF into a single component as DOC-on-filter instead of separate DOC and DPF substrates to achieve space saving has been previously discussed in literature. This study expands on the current understanding and explores various functional performance characteristics of the DOC-on-filter concept in comparison with DOC + bare DPF, DOC + PGM coated DPF. The three test configurations were evaluated for pressure drop, filtration efficiencies, active and passive regeneration performances. Relative advantages and challenges of each configuration were discussed. Along with a current Tier 4F filter, a next generation filter was introduced for performance understanding in non-road applications. Pressure drop of DOC-on-filter was comparable to other test configurations within a given filter product. Significant improvements in filtration were achieved by the next generation filter compared to the current Tier 4F filter for bare, PGM coated, and DOC-on-filter coated filters. DOC-on-filter performance was found to be equivalent to other configurations in passive regeneration test conditions, however, it performed poorly in active regeneration test conditions. Better active regeneration efficiency of DOC-on-filter may be achieved by longer regeneration durations but that may lead to significant penalty in fuel economy. DOC-on-filter technology was found to be a viable technology pathway with certain limitations for applications which primarily depends on active regeneration of filters.